Modern surfboards desirably include a fin adjacent the tail thereof, and along the centerline of the board, to provide dimensional stability, to maximize board performance. While conventional fins are certainly useful for that purpose, they pose two significant problems. One is that the fin can be dangerous to surfers or nearby swimmers if the surfboard is travelling at high speed and the leading or trailing edge of the fin hits the surfer or swimmer. Also, while providing good dimensional stability, a fin may, depending upon the circumstances, restrict maneuverability.
According to the present invention a surfboard fin, and a surfboard, are provided which overcome the problems inherent in the prior art. According to the most basic aspects of the present invention, a surfboard fin or fins are provided which have soft, flexible leading and trailing edges so that if they impact a surfer or swimmer the injury will be minimized. The flexible material at the trailing edge of the fin or fins also provides a rudder action to provide maneuverability to a surfer standing on the top surface of the board and shifting his/her weight. Although numerous advantages are obtained by utilizing a single tail fin, preferably a plurality of fins are provided, e.g. three fins spaced at particular locations adjacent the tail of the board.
According to one aspect of the present invention a surfboard tail fin is provided comprising: A rigid body element having a leading edge, and a trailing edge; and a flexible material covering disposed on the leading and trailing edges of the rigid body element. The flexible material is soft enough to minimize injury to a person impacted by a leading or trailing edge of the fin, and is flexible enough to be deflected by water pressure during surfing to provide a rudder action. Preferably the rigid body element is of a hard plastic having a Shore D hardness of at least about 60 an preferably at least about 78), while the flexible material is a soft plastic (such as a urethane or silicone) having a Shore A hardness of about 40-100 (preferably about 40-94), a thickness on the trailing edge of at least about 0.25 inches, and a thickness on the leading edge of at least about 0.1 inches.
According to another aspect of the present invention a surfboard is provided having a top surface and a bottom surface, a front end (nose), and a rear end (tail). The surfboard includes at least one tail fin extending downwardly from the bottom surface adjacent the rear end. The fin comprises a rigid body element having a leading edge, and a trailing edge; and a flexible material covering disposed on the leading and trailing edges of the rigid body element, the covering material having sufficient thickness, softness and flexibility to minimize injury to a person impacted by a leading or trailing edge of the fin, and to be deflected by water pressure during surfing to provide a rudder action (anti-cavitation action) as a surfer shifts his or her weight on the top surface of the surfboard.
The surfboard according to the invention has a centerline between the front and rear ends, and preferably has three fins. A first fin is provided closest to the tail and disposed on the centerline, with the second and third fins disposed further from the tail than the first fin and off the centerline. The second and third fins are disposed approximately the same distance from the tail as each other and approximately the same distance from the centerline and on opposite sides of it, and have flat inner side faces. The leading and trailing edges of the first fin are substantially coplanar with the center plane containing the centerline. The second and third fin leading and trailing edges are in planes which makes a slight angle (e.g. about 2.degree.-10.degree.) to the centerline, the leading edges being slightly closer to the centerline than the trailing edges. Also the center plane is substantially vertical when the board is in use, while the planes containing the leading and trailing edges of the second and third fins are slightly off vertical (e.g. about 2.degree. to 15.degree.).
The fins according to the invention may be manufactured by a wide variety of techniques, including by molding both the rigid and the flexible plastics together at the same time; injection molding the flexible plastic onto the rigid plastic once it has been formed (the preferred manner); or cutting and contouring sheets or strips of flexible material and adhesively connecting them to the edges of the rigid material. The fins may be connected to the surfboard by conventional techniques utilizing fiberglass rope and fiberglass cloth impregnated in resin, the fiberglass rope extending along all portions of the enlarged base of the rigid plastic element of the fin, while the fiberglass cloth extends up along the sides of the rigid plastic portion of the fins. The fin sides can be concave where they receive the fiberglass, and have ridges which protect the flexible material edges of the fin.
Alternatively, the fin can be removable, e.g. mounted in a conventional fin box.
It is the primary object of the present invention to provide a surfboard fin, and surfboard containing at least one fin, having enhanced safety and maneuverability characteristics. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.